Mall of America "extra security precautions" after threat

A Somali al Qaeda affiliate's call for attacks on shopping centers in Western countries singled out one American mall in particular: the Mall of America in Bloomington, Minnesota.

The largest mall in the U.S. has responded by taking "extra security precautions - some visible to guests and others that are not," a security official there told CBS News.

The official said they will continue to work closely with the FBI and the Department of Homeland Security and that they will "remain diligent as they would do in any similar situation."

Earlier, Homeland Security Secretary Jeh Johnson said shoppers at the Mall of America need to be "particularly careful," after Somali terror group Al-Shabaab called for attacks.

In an online video Saturday, the group also singled out the West Edmonton Mall in Alberta, Canada, and London's Oxford Street.

Federal law enforcement officials told CBS News that they are investigating the video, but added that so far al-Shabaab has not demonstrated an ability to launch major external operations outside East Africa.

In 2013, the Somali-based group claimed responsibility for an attack on an upscale shopping mall in Kenya.

More than 60 people were killed in the four-day siege when attackers stormed the Westgate Mall in Nairobi.

CBS News correspondent Charlie D'Agata reports that the video released Saturday begins with the focus on the 2013 attack. It is a documentary-style video that runs more than an hour long, focusing on Kenyan forces and their intervention into Somalia.

The group is essentially saying if militants can attack a mall in Nairobi then others can attack targets elsewhere, D'Agata reports.

U.S. law enforcement officials tell CBS News their posture has not changed with the release of the video. The mall attack in Kenya had already led to a new sense of urgency and a review of tactics in case of a similar attack.

Local police in major cities cities like Chicago and New York across the country have been notified of this threat from Al-Shabaab by the Department of Homeland Security, officials tell CBS News.